Carbon dioxide gas, used in carbonated beverages, in food packaging, and in disinfection, is occasionally found, at the point of use, to be contaminated with compounds that can affect the taste, smell, and even the safety of the food or beverage product with which it is being used. The numerous, often localized, processes of manufacturing or acquiring carbon dioxide gas are often imperfect in their ability to generate fully pure carbon dioxide, and methods of cleaning or “scrubbing” the gas occasionally fail. Pure carbon dioxide can then become contaminated upon storage or transport, particularly if it is placed in previously contaminated containers.
Contaminated carbon dioxide can contain a wide range of contaminants, including acetaldehyde, sulfur compounds, aromatic hydrocarbons like benzene, and other volatile hydrocarbons like methane. Most contaminants, in moderate levels, only result in negative taste and smell impacts to the products using the carbon dioxide. In high levels some contaminants are toxic and can cause illness and even death. Benzene and a few others are, in moderate levels, believed to be carcinogenic.
The International Society of Beverage Technologists (ISBT), a beverage industry organization with over 1,000 corporate members, has developed guidelines for acceptable contamination levels in nonalcoholic beverages and soft drinks. These guidelines recommend maximum concentration levels for thirteen compounds or compound families including, for example, that acetaldehyde concentrations never exceed 200 parts-per-billion and that aromatic hydrocarbon concentrations never exceed 20 parts-per-billion.
However, the continuous or near-continuous monitoring of carbon dioxide in a production environment is currently very costly. Carbon dioxide analyzers on the market are built around chemical analysis equipment employing gas chromotography (GC) and mass spectroscopy (MS), more commonly found in laboratories. Carbon dioxide analyzer companies ruggedize these GC/MS units and augment them with peripheral electronic equipment to regulate sample flow and automate their measurement functions. These systems can easily cost $200,000 or more. They comprise one or more racks of equipment in an enclosure that can be five or six feet tall and weigh hundreds of pounds.
In addition to their high cost, current carbon dioxide analyzers are often touchy and expensive to maintain. Some require the use of “carrier” gases, including hydrogen, which is highly explosive. Carrier and “span” gases used in calibration can routinely cost $6,000 per year. The units typically sample the carbon dioxide flow at a rate of once every ten to twenty minutes, which may not be fast enough to catch fast contaminant transients, or eliminate all chance of product contamination.
Therefore, there is a need for a compact, robust, and inexpensive monitor that can make accurate and near-real-time measurements, thus dramatically reducing cost while enabling carbon dioxide producers and users to better assess and reduce contamination risk.